I wanted to get a much wider tire, so I also had to get different wheels, and if you’re going to get new wheels why not make them nice and shiny!

This is a before photo with the stock wheels/tires.

So a few weeks ago I decided to do a test, and see just how far I could drive on a full tank of gas with the Prius. I wanted to find out, definitively, how far I could drive once the “add gas now” warning started to flash. Here are the details.

The tank holds 11.9 gallons, but from what I’ve read online it’s difficult to fill the tank completely. There is a bladder inline between where you fill the tank and the tank itself to prevent fumes from escaping. The down side is you end up only fitting about 10.9 gallons in the tank.

The Details
I used regular unleaded, 87 octane.

The miles are 90% highway, since the vast majority were on the drive to and from the office, which is just short of 50 miles round trip every day.

On the highway I would use the cruise control and set it to 55. The Prius seems to be tuned to get it’s peak mileage at 55, and the cruise control does a much better job and managing the overall mileage then if you try to do it yourself.

I had a one gallon tank of gas in the trunk, ready for the refill once I ran out.

So, the results?

After almost 2 weeks of driving, I coasted to a stop having drove 587miles, but not the 600 I was shooting for.

The computer said that my fuel mileage was 53.8 for that tank, but if you do the math based on the 11.9 gallon tank it’s more like 49 mpg. Again though, taking into account that it really only holds 10.9 the mileage is 53.8, exactly what the computer reported!

No matter how you cut it, it’s a lot better then the 16mpg I was getting on the Toyota Sequoia (but I will admit that I LOVED that truck).

Some More Math
So, what’s the difference in gas cost over a year?

I know that I drive about 20K miles per year. If on a year round average I get about 48 mpg on the Prius (mileage in the winter is usually in the high 30′s, not the 50′s) and 16 in the Sequoia (which was the same year round), what would the difference in cost be based on the current price of $2.88 per gallon?

Over 5 years, you will spend $6,000 on gasoline for the Prius, and $18,000 on the Sequoia. That’s $12,000 ($200 per month) more out of your pocket and directly to the oil companies! I don’t know about you, but I can think of better things to do with my money.

And this does not even take into account the high likelihood that gas prices will continue to rise. Do the same math at $4 per gallon and the gap gets even wider.

I’m sharing this last part because it’s this calculation that made me realize we needed to trade the truck in for something better on gas. Just seeing the numbers on paper was enough for me to know immediately that something had to change. When gas was less then a dollar a gallon I didn’t care, but now I really do.

The good news is, that in 5 years the overall mileage of cars in general should be much better, and hybrid vehicles will be a lot more common.